No, the Red Sox shouldn't make a snap decision on a Rule 5 pick do to some rookie mistakes. If every team was so quick to judge, no pick would ever stick on a big league club. Considering the lack of quality minor league OF depth, the team can't really afford not to hold onto Stern.
Yeah, it's sucked that he's gotten picked off, but if his strength really is his baserunning, why in the world would you not attribute the gaffes to jitters?
And you're not putting in a worse bat when you pinch run Millar for Stern. You're putting in a better baserunner (believe it or not), while upgrading defensively at first (when Olerud isn't DL'ed) or at the very least putting in a bat that could be expected to do as well as Millar has this season (Petagine).
And sorry to nitpick, but it's "Rule 5".